PID settings

[TimG]

Hey guys,

So gearing up my mash tun PID controller (1500W 120V element, yes I will have to plan ahead to heat the water). Looking for a decent starting point for the PID settings. I'm aware I can do 'autotune' but with my initial testing so far I haven't had much luck getting my unit to work (it's the cheaper Sestos version not an official Auber).

Thanks!

[RubberToe]

It won't autotune at all?

Describe your mash tun, element and temp probe placement, etc.

You probably won't have much luck with other people's PID settings unless they're using the same Sestos unit.

[mr x]

Sometimes those autotunes will time out if they haven't seen enough temp change, which can happen on larger tanks.

[TimG]

Ya, I think that's what happened.. I was testing it with a shitty little slow cooker and the temp change too FOREVER! I'm going to be using a 1500W 120V element placed in the bottom corner of my big ass 100L cooler (BIAB hybrid). Obviously the temp change will be different for different water volumes (super slow for a 10g batch, faster for 5 g). So maybe I just put in 35L and let it go and see what happens?
I'll be able to fire it up tonight, so I guess I'll just try autotune again and see how it goes.

Thanks

[RubberToe]

Yeah it doesn't make any sense to autotune with the slow cooker, you need to do that in your final setup as there are different factors that effect the settings.

[mr x]

Yeah, throw in a smaller batch of water and see what happens.

[TimG]

Ya I wasn't trying to use the slow cooker to autotune for my cooler.. I just wanted to try some sous vides eggs!

I'll report back on my autotune attempts tonight.

[gyorke]

One gotcha with the Sestos units and the Chinese SSRs is they don't work well with a cycle time less than 4s. Mine was running crazy until a lot of Googling suggested I change the cycle time back to the default of 4s. Then the autotune worked fine.

[TimG]

Thanks for the tip, I don't think I changed it from default but I'll check. Is the cycle time one of the P , I , or D settings?

Tim

[RubberToe]

t on Auber at least.

Sent from the brew timer.

[TimG]

Turns out it's Ctrl on the Sestos. So the testing has been going ok.. in that the element install doesn't leak, happy with my junction box install (nice and clean). But.. the size of the cooler simply 'demands' some sort of mixing during heating. A simple aquarium pump might be good? Or should I rig up a simple mixer with a low rpm motor (120V preferred).

Also, wondering if I shouldn't have it running after the temp is reached (for example.. with my hand stirring the temp came up fast, but now is sitting 2-3degC over my temp and I bet it'll take a long time to drop, due to the insulated cooler).

Guess I'll leave the autotune go and see if it 'finishes'. I'd have to do it all over again anyways once I rigged up a mixer.

Work in progress..

[HPhunter]

I find that PID control on under powered things is a pain in the ass. All the cycling is a load on everything and unnecessary if underpowered. It will actually slow down the process a lot. Try switching it to on/off with a way of circulating and see if it works better. That's been my experience anyway.

[TimG]

Ya.. I'm thinking maybe the overshoot would be very minimal if I just used a simple STC controller. Hmm.. building this PID might have been a bit of a waste, ha. Hopefully I can get it working for sous vides!

I could just have my set temp a couple deg C less than my strike temp and bring it up right before I mash in. Getting some movement in the water is going to be key.. be nice to find a simple low rpm 120V super light duty motor. Do they exist? Maybe a small cooling fan motor?

[bluenose]

Turns out it's Ctrl on the Sestos. So the testing has been going ok.. in that the element install doesn't leak, happy with my junction box install (nice and clean). But.. the size of the cooler simply 'demands' some sort of mixing during heating. A simple aquarium pump might be good? Or should I rig up a simple mixer with a low rpm motor (120V preferred).

Also, wondering if I shouldn't have it running after the temp is reached (for example.. with my hand stirring the temp came up fast, but now is sitting 2-3degC over my temp and I bet it'll take a long time to drop, due to the insulated cooler).

Guess I'll leave the autotune go and see if it 'finishes'. I'd have to do it all over again anyways once I rigged up a mixer.

Work in progress..

[gyorke]

Not sure if you had the overshoot while running the autotune or when actually mashing but you should expect the autotune to overshoot. From my reading it is part of the process.

[TimG]

Yes I had overshoot, and I agree that it is supposed to happen during autotune. My overshoot comment was more in regards to not bothering with the PID for the mash water, just using a simple STC controller (which will for sure overshoot.. but the low power and significant mass of the water in the tun, I'm guessing it won't be significant). As HP pointed out, I'm just wasting energy with the PID (heating up the SSR) running it full blast for the 'long' time it is going to take to heat up my mash water.

[TimG]

I have a GFCI receptacle installed in my PID cotrol box. Currently the SSR controls both top and bottom 'ports', is it possible for me to wire the SSR to one port and a simple STC (on/off relay) controller to the other port?

Thanks!

[gyorke]

All of the gfi receptacle I have seen only have one set of power in connections so there would be no way to power the two outlets separately. You would need to add another receptacle, but you could still use the gfi in the box and have it protect one side of that normal receptacle.

[Jayme]

If you switch to the stc, consider a mechanical relay. If you're under powered to start, and SSR is just wasting more energy compared to a mechanical relay. Pretty easy to compensate for the overshoot also. Just figure out the offset one time and you're golden.


Sent from a rotary telephone using taps talk

[TimG]

Isn't the STC essentially already a mechanical relay?

[Jayme]

Yes a small one. I think it's 10amps... Been a while since I opened one up. You should have at least 15A for 1500w at 120v. That's 12.5A, though a little less for 110V. At work our design spec is to de rate relays to 75%.


Sent from a rotary telephone using taps talk

[TimG]

I actually was planning on using one of the 'even cheaper' STC type controllers that only do hot or cold (and only 1 deg C accuracy). I opened it up and it says 15A for 12V so all good. I'll let you know how it works. Good point about planning for the overshoot. I should log the temp a few times and should be able to plan for the overshoot for various water volumes.

[TimG]

Few pictures of the PID setup (which I'm likely not going use now.. heh) and my heating element install









This last one is my new mash water stirring device.. a $10 ice cream maker, old school, made in the US 'way' back in the day. Spins at 60 rpm apparently, which I think will work out. May try to slow it down or only run it one minute out of every 3 or something.